L-phenylalanine effect on rat brain acetylcholinesterase and Na+,K(+)-ATPase

The effect of different L-phenylalanine (Phe) concentrations (0.1-12.1 mM), on acetylcholinesterase (AChE) and Na+,K(+)-ATPase activities of brain homogenate and pure enzymes, was investigated at 37 degrees C. AChE and Na+,K(+)-ATPase activities were determined according to Ellman G. L., Courtney D., Andres V. and Featherstone R. M. (1961), Biochem. Pharmacol. 7, 88-95 and Bowler K. and Tirri R. (1974), J. Neurochem. 23, 611-613) respectively, after preincubation with Phe. AChE activity in brain homogenate or in pure eel E.electricus enzyme showed a decrease, which reached up to 18% with concentrations of 0.9-12.1 mM. Brain homogenate Na+,K(+)-ATPase activity showed an increase 16-65% with 0.24-0.9 mM of Phe, while an activity increase of 60-65% appeared with 0.9-12.1 mM of Phe. Pure enzyme activity (from porcine cerebral cortex) was not affected by high Phe concentrations, while it was increased by low concentrations. The above results suggest: a) A direct effect of Phe on AChE, b) A direct effect of low Phe concentrations and an indirect effect of high ones on Na+,K(+)-ATPase.